You know how, before a movie starts, the theater puts up a little “don’t be a jerk” reminder on the screen? At my local theater, it says, “Please be quiet and courteous to others, and silence your cellphones.”

What if the opposite were true? What if, before a movie began, the theater said, “Please talk throughout the movie, to yourself and your friends. We want to hear from everyone!”

That’s what watching a movie on Amazon’s newly-bought video streaming site Twitch is like. And, astonishingly, it kind of works.

I tuned in Wednesday evening at a pre-announced time (appointment viewing: not dead yet) to watch “State of Play,” a 2013 documentary about the professional eSports scene in South Korea, where Blizzard’s Starcraft games are an unofficial religion. As an on-screen countdown to the movie ticked to zero, there were about 2,000 people watching, according to the counter below the video.

“Never watched a movie with a bunch of strangers online before,” one commenter in the chat adjacent to the video said. “Weird.”

“Geez, some dude has his phone on in the theater,” another chimed in.

Jokey commentary lasted for all 85 minutes of “State of Play,” though spotting it required a practiced focus. Rather than leaning back in my chair, I found myself perched at my desk, my eyes darting between the movie (subtitled in English) and the chat to see what the Twitchers had to say next. It was like an anarchic amateur version of “Mystery Science Theater 3000.”

Since anyone could comment, there was a lot of garbage to sift through to get to the good stuff. When two players were massaging each other before a game, the chat erupted into calls of “haaa gaaay” and “asian gay porn?” Pretty much any time a woman appeared in the film, viewers would interject “hot,” “MILF,” “omg a girl,” or — something that appears to be an established meme on the site — “GRILL.”

The immature comments speak to how young Twitch’s audience is. The average age of users on the site is 21, and 24 percent are under 18. They also underscore how deeply hooked into the site’s “community” they are, posting the first thing that comes to their minds, a stream-of-consciousness race to shout into the abyss.

On the flip side, that same mind dump yielded some hilarious results. Twitch Emotes, a popular emoji-like shorthand on the site, are little faces fashioned after game characters and Twitch employees, and each has its own meaning.

“They represent a deeper meaning for the community and are essentially the language of Twitch,” content marketing director Ben Goldhaber said via email. “These are often based upon the channel’s own narrative or community in-jokes.”

Most of the jokes flew over my head — in the past, I’ve mostly avoided Twitch chat except to play Pokémon — but even a n00b could appreciate the torrent of sleeping emotes when the camera focused on a sleeping player, or the crying faces that poured in when the documentary turned sad.

It’d be easy to dismiss this alternative language and other slight comments out of hand, but it says something important: These viewers were clearly paying attention to the movie, and rewarded one another for proving that they were paying attention. Talking about this shared experience, on a site typically dedicated to broadcasting videogames, was a game itself.

This is not far off from the idea of “social television” that the TV guys have been talking about for ages — using social platforms like Twitter and Facebook to enhance the viewing experience. But on those sites, you’re generally talking within your own social circles, on platforms not explicitly designed for those conversations. Twitch’s chat is optimized for quick reactions to a live event, in an arena where every voice is heard.

Of course, not all those voices showed up on time. The stream I watched climbed from 2,000 concurrent viewers at the start to 3,600 ten minutes in, ultimately topping out at around 6,300 near the half-hour mark. About 45 minutes in, one commenter asked if the documentary had started yet, to which one person said that yes, it started two minutes before.

Still, Goldhaber said Twitch’s non-game streams have succeeded in drumming up buzz in the movies, shows and events being broadcast.

“I reached out to ‘State of Play’ and many of the initial film producers that have worked with us for live airings, but now many are organically reaching out to us,” he said. “We work directly with the content creators to make sure this is a mutually beneficial initiative.”

He declined to commit to a regular schedule for similar broadcasts, but added that “we expect this to become a more regular form of content on Twitch.”